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Two databases on one instance

I would be very grateful if someone could confirm whether it is recommended to have two databases running on one instance and what are the security risks and disadvantages of having 2 databases on one instance.

The answer to that questions depends on the applications that you are trying to run. If both applications use public synonyms,
then they could conflict, if they are being run for different departments and you need to keep a clear separation of duties, then
unless you have really good security people might get access to objects that they should not have access to.

Ideally if they really are two different applications then you probably want to run one application per instance.That would make
it easier to clone one of the databases to a test instance, without having to clone everything. Just make sure that your server
has enough memory and enough processor cores.

I would be very grateful if someone could confirm whether it is recommended to have two databases running on one instance and what are the security risks and disadvantages of having 2 databases on one instance.

Thank You

Before this question can be answered, you may first have to read the definition of Database and Instance in the fine OracleŽ Database Concepts book and then maybe ask the correct question.

"The person who says it cannot be done should not interrupt the person doing it." --Chinese Proverb

Recently i seen this kind of scenario, a manufacture using two different database in two different location , both are different versions [9i & 10g], they planned to upgrade both into 11gR2 and wanted to run in one instance. because they are not able to maintain two different database in different locations.[Yes both database are accessed by different applications]

Kindly suggest me what we can do in this kind of Scenario. what i am expecting is to export both dump files into 11gR2 instead of upgrading both DB's, there is no similarity between the old db's except their system tablespaces. so in import there wont be any issues or conflicts..

I would be very grateful if someone could confirm whether it is recommended to have two databases running on one instance and what are the security risks and disadvantages of having 2 databases on one instance.

Thank You

What do you mean by instance? You mean on one server or do you really mean 2 databases on one oracle instance?

Your statement does not make any sense.
Please join with skhulput12 and read the fine book: OracleŽ Database Concepts.
PS: "Database" in SQL server "speak" is NOT the same as in Oracle "speak".

Boss,, i said two different DB in two Different location.
Its a location change process. Physical Location Change of Servers at the same time they wanted to run with upgraded version of Oracle and Server..

I did not asked about any one instance & two database Questions,, why u getting this much rude senior,,, Kindly read my second paragraph of my Export/Import Q's and update me Dear Sir..

Recently i seen this kind of scenario, a manufacture using two different database in two different location , both are different versions [9i & 10g], they planned to upgrade both into 11gR2 and wanted to run in one instance. because they are not able to maintain two different database in different locations.[Yes both database are accessed by different applications]

Kindly suggest me what we can do in this kind of Scenario. what i am expecting is to export both dump files into 11gR2 instead of upgrading both DB's, there is no similarity between the old db's except their system tablespaces. so in import there wont be any issues or conflicts..

Am i correct kindly update me..

Regards
Hamid

I think in this you can do 2 things if you want to run it on one location and one server:

- You can use one instance and import all in it which makes you having less maintenance on the database itself.
- You can create 2 instances for the different applications which is more maintenance on the instances itself but you have more flexibility.

As already mentioned in a way above, from security perspective you should be aware of the fact that with 2 applications you will have probably more different users on 1 database who have access.

Also the amount of data you have to move from one instance to another (for instance a testenvironment) is more difficult. Although you can make a specific export for a specific amount of data it is more work and more time consuming I would say.

If you should choose for 1 new instance make sure that there are no parameters in the old databases that differ in a way that you will have performance issues.

For the Oracle software itself it doesn’t matter as maintenance on that is a one time action(like patching) that goes for both situations.

For all above of course it is inevitable to have proper sized hardware.
In this situation it will be 1 database/1 instance or 2 databases/2 instances assuming that it is not a RAC environment.